How long would it take for a novel alelle to be fixated in a population?

Unless selection is very intense the number of deaths needed to secure the substitution by natural selection, of one gene for another at a locus, is independent of the intensity of selection. It is often about 30 times the number of organisms in a generation. It is suggested that in horoletic evolution, the mean time taken for each gene substitution is about 300 generations. This accords with the observed slowness of evolution.

Imagine a population of 100,000 apes, the putative progenitors of humans. Suppose that a male and a female both received a mutation so beneficial that they out-survived everyone else; all the rest of the population died outall 99,998 of them. And then the surviving pair had enough offspring to replenish the population in one generation. And this repeated every generation (every 20 years) for 10 million years, more than the supposed time since the last common ancestor of humans and apes. That would mean that 500,000 beneficial mutations could be added to the population (i.e., 10,000,000/20). Even with this completely unrealistic scenario, which maximizes evolutionary progress, only about 0.02% of the human genome could be generated. Considering that the difference between the DNA of a human and a chimp, our supposed closest living relative, is greater than 5%,2 evolution has an obvious problem in explaining the origin of the genetic information in a creature such as a human.

Haldane calculated that no more than 1,667 beneficial substitutions could have occurred in the supposed 10 million years since the last common ancestor of apes and humans. This is a mere one substitution per 300 generations, on average.